Dissertations / Theses on the topic 'Shock absorber (damper)'

Semi-active suspension systems promise to significantly reduce the necessary trade-off be-tween handling and passenger comfort present in conventional suspension systems by enabling active chassis and wheel control. Öhlins Racing AB have developed a semi-active suspension technology known as CES, Continuously controlled Electronic Suspension, based on solenoid control valves which are integrated into specially designed hydraulic dampers, and are currently developing control and estimation systems which will enable their application in advanced motorcycle suspensions. In these systems an important aspect is being able to accurately control the forces produced. Öhlins’ current system uses an open loop control strategy in which currents sent through the solenoid valves, to achieve the requested damping force under the prevailing circumstances, is calculated using experimentally derived static lookup tables. In this thesis a new closed loop control system, based on the direct measurement of the damper force, is developed and its performance is evaluated in comparison to the old one’s. Sufficient understanding of the system requires extensive modeling and therefore two different models have been developed; a simpler one used for model based control design and a more extensive, high fidelity model used for high accuracy simulations. The developed simulation model is the first of its kind that is able to capture the studied systems behavior with satisfactory accuracy, as demonstrated against real dynamometer measurements. The valves and damper behave in a highly non linear manner and the final controller design uses a combination of exact linearization, non linear state estimation, dynamical inversion and classical control theory. Simulation results indicate that the new controller reduces the root mean square force tracking error to about 63% of that of the existing controller in the evaluation scenarios used. Cascaded within the system is also closed loop current controllers. A developed model based controller is shown to reduce the rise time to less than 30% of that of the existing PID-controllers, reduce the overshoot and provide online estimates of the winding series resistance, providing the basis for future solenoid diagnosis and temperature tracking systems.

This thesis describes the implementation of a parametric model of an automotive damper. The goal of this research was to create a damper model to predict accurately damping forces to be used as a design tool for the Formula SAE racecar team. This study pertains to monotube gas charged dampers appropriate to Formula SAE racecar applications. The model accounts for each individual flow path in the damper, and employs a flow resistance model for each flow path. The deflection of the shim stack was calculated from a force balance and linked to the flow resistance. These equations yield a system of nonlinear equations that was solved using Newton's iterative method. The goal of this model was to create accurately force vs. velocity and force vs. displacement plots for examination. A shock dynamometer was used to correlate the model to real damper data for verification of accuracy. With a working model, components including the bleed orifice, piston orifice, and compression and rebound shims which were varied to gain an understanding of effects on the damping force.

Magnetorheolgical (MR) fluid dampers have the capability of changing their effective damping force depending on the current input to the damper. A number of factors in the construction of the damper, as well as the properties of the fluid and the electromagnet, create a dynamic response of the damper that cannot be fully described with a static model dependent on current and velocity. This study will compare different techniques for modeling the force response of the damper in the current-velocity space. To ensure that all the dynamic response characteristics of the damper are captured in data collection, random input signals were used for velocity and current inputs. By providing a normally distributed random signal for velocity to a shock dynamometer and a uniformly distributed random signal for current to a Lord rheonetic seat damper, the force response could be measured. The data from this test is analyzed as a two dimensional signal, a three dimensional force plot in the current velocity plane, and as a probability density function. Four models are created to fit the data. The first is a linear model dependent solely on current. The second is a nonlinear model dependent on both current and velocity. The third model takes the nonlinear model and includes a filter that affects the force response of the model with time. Each of these three approaches are compared based on the total error in the force response and the models? ability to match the PDF of the data. Finally, a fourth model is created for the damper that improves the nonlinear model by making one parameter a probability parameter defined by a PDF calculated from the data. However, because it is a probability model, the error cannot be found through comparison to the data.
Master of Science

In recent years, a flurry of interest has been shown for a relatively old technology called magneto-rheological fluids, or MR fluids. Multiple types of devices have been designed to implement this versatile fluid, including linear dampers, clutches, work-piece fixtures, and polishing machines. The devices have been used in automobiles, washing machines, bicycles, prosthetic limbs, and even smart structures. This thesis focuses on another application of MR dampers, involving super-sport motorcycles. This paper introduces the topics of MR dampers and motorcycle suspensions, and why the two would be a good combination. A detailed history of MR fluids, MR dampers, and motorcycle suspension technologies is given next. After a broad outline of MR dampers and motorcycle suspensions, the method of designing and manufacturing MR dampers is discussed. The damper design for this research is presented in detail, along with the design procedure used to make it. Next, laboratory testing for it is covered, including the test equipment, test procedure, and the laboratory test results. Upon laboratory test completion, the field test setup and procedure are presented. The results of field tests with stock dampers and MR dampers with a variety of control systems is discussed. The MR dampers provided a more stable ride than that of the OEM dampers. By reducing suspension displacement, settling time, and suspension oscillations, the MR dampers were able to reduce suspension geometry instability. Lastly, concluding remarks are made on the research presented. Design flaws are discussed, as well as recommendations for future work in the same area.
Master of Science

Investigations on the design of controllable magnetorheological (MR) fluid devices have focused heavily on low velocity and low frequency applications. The extensive work in this area has led to a good understanding of MR fluid properties at low velocities and frequencies. However, the issues concerning MR fluid behavior in impact and shock applications are relatively unknown. To investigate MR fluid properties in this regime, MR dampers were subjected to impulsive loads. A drop-tower test facility was developed to simulate the impact events. The design includes a guided drop-mass released from variable heights to achieve different impact energies. Five drop-heights and two fundamental MR damper configurations were tested. The two configurations were a double-ended piston and a mono-tube with nitrogen accumulator. To separate the dynamics of the MR fluid from the dynamics of the current source, each damper received a constant supply current before the impact event. A total of five supply currents were investigated for each impact velocity. After reviewing the results, it was concluded that the effect of energizing the MR fluid only leads to â controllabilityâ below a certain fluid velocity for the double-ended design. In other words, until the fluid velocity dropped below some threshold, the MR fluid behaved as if it was not energized, regardless of the strength of the magnetic field. Controllability was defined when greater supply currents yielded larger damping forces. For the mono-tube design, it was shown that the MR fluid was unable to travel through the gap fast enough during the initial impact. Consequently, the damper piston and accumulator piston traveled in unison until the accumulator bottomed out. After which, the fluid was forced through the gap. In conclusion, the two designs were compared and general recommendations on designing MR dampers for impulsive loading were made. Possible directions for future research were presented as well.
Master of Science

Successful race teams rely heavily on track testing to search for the ideal suspension setup. As more restrictions are placed on the amount of on-track testing by major racing sanctioning bodies, such as NASCAR, teams have increased their attention to alternate testing methods to augment their track data and better understand the dynamics of their racecars. One popular alternate to track testing is 8-post dynamic shaker rig testing. Eight-post rig testing gives the team a better understanding of the vehicle's dynamics before they arrive at the race track, allowing them to use their limited track testing time more efficiently. While 8-post rig testing certainly is an attractive option, an extensive test matrix is often required to find the best suspension setups. To take full advantage of 8-post rig tests, more efficient experimental methods are needed. Since investigating shock absorber selection is often the most time-consuming task, this study focuses on developing more efficient methods to select the best shock absorber setups. This study develops a novel method that applies dynamic substructuring and system identification to generate a mathematical model that predicts the results of future tests as both command inputs and components are changed. This method is used to predict the results of 8-post rig tests as actuator commands and shock absorber forces are varied. The resulting model can then be coupled with shock absorber models to simulate how the vehicle response changes with shock absorber selection. This model can then be applied to experimental design. First, a physically-motivated nonlinear dynamic shock absorber model is developed, suitable for quickly fitting experimental data and implementing in simulation studies. Next, a system identification method to identify a vehicle model using experimental data is developed. The vehicle model is then used to predict response trends as shock absorber selection is varied. Comparison of simulation and experimental results show that this model can be used to predict the response levels for 8-post rig tests and aid in streamlining 8-post rig testing experimental designs.
Ph. D.

Магістерська дисертація на тему “Удосконалення ендопротезу колінного суглобу за рахунок використання магнітно-реологічного демпфера”, складається з __3__ розділів, обсяг пояснювальної записки __117__ сторінок основного тексту, включає _75__ рисунків і _31__ таблиця, та __8__ плакатів графічного матеріалу. Метою роботи є підвищення стабільності МРД протезу колінного суглобу в змінних умовах експлуатації. Для досягнення поставленої мети було сформульовано ряд задач: - провести аналіз існуючих конструкцій протезів колінних суглобів; - теоретично обґрунтувати та створити математичні моделі робочих процесів та дослідити вплив температури та напруженості магнітно поля на робочі характеристики МРД; - розробити експериментальну установку для перевірки та уточнення математичних моделей МРД; - провести експериментальні дослідження; - розробити рекомендації щодо створення адаптивних демпферів з урахуванням результатів отриманих при виконанні роботи. Перший розділ даної роботи присвячено аналітичному дослідженню впливу зовнішніх та внутрішніх факторів на демпфери протезу та методи адаптації під них. Другий розділ присвячено розробці математичної моделі яка описує залежність впливу температури на робочу характеристику демпфера. Третій розділ включає в себе створення стенду для проведення відповідних експериментальних досліджень, представлена схема та необхідна апаратура, що дозволили створити безпосередньо стенд для досліджень впливу температури та тиску робочого середовища на робочі характеристики МРД суглобу. Розробити методи експериментальних досліджень. Проведено серії експериментів, для визначення впливу перепаду тиску та температури на робочу характеристику. Об’єктом дослідження в даній роботі є процес функціонування МРД протезу колінного суглобу, а саме його дроселя при різних умовах експлуатації. Предметом дослідження є зв'язок конструктивних параметрів провідності регульованого дроселя та зміни температури робочої рідини. Науковою новизною даного дослідження є запропоновані аналітичні залежності, що відображають зміну витрати від прикладеної сили струму (магнітного поля). Розроблена уточнена математична модель процесу демпфування протезу колінного суглобу. Перелік ключових слів: Демпфер, протезування, моделювання в SolidWorks, адаптивні властивості, дросель. Для дослідження МРД використовувався пакет прикладних програм „MatLab ”, в додатку до нього „Simulink”. Результати дослідження дозволяють вдосконалити конструкцію МР демпфера та зменшити температурний фактор на його характеристики. Публікаціїї. За матеріалами магістерської дисертації було опубліковано 4 праці, а саме 3 тези доповідей на міжнародних науково-технічних конференціях студентів.
The master's thesis on the theme "Improvement of knee joint endoprosthesis due to the use of magnetic-rheological damper" consists of __3__ sections, the volume of the explanatory note __117__ pages of the main text, includes _75__ drawings and _31__ tables, and __8__ posters of graphic material. The aim of the work is to increase the stability of the MRI of the knee joint prosthesis under varying operating conditions. To achieve this goal, a number of tasks were formulated: - to carry out an analysis of existing designs of knee joints; - theoretically substantiate and create mathematical models of work processes and investigate the influence of temperature and intensity of the magnetic field on the operating characteristics of the MRD; - to develop an experimental installation for checking and refinement of mathematical models of MRD; - to conduct experimental research; - to develop recommendations for the creation of adaptive damping taking into account the results obtained during the work. The first section of this paper is devoted to the analytical study of the influence of external and internal factors on the denture dampers and the methods of adaptation under them. The second section is devoted to the development of a mathematical model that describes the dependence of temperature influence on the performance of the damper. The third section includes the creation of a stand for conducting relevant experimental research, a diagram and the necessary equipment are presented, which allowed to create a stand directly for research on the influence of temperature and pressure of the working environment on the working characteristics of the MRD of the joint. Develop experimental research methods. A series of experiments was conducted to determine the effect of pressure drop and temperature on the performance. The object of the research in this paper is the process of functioning of the MRI of the knee joint prosthesis, namely, its chokes under different operating conditions. The subject of the study is the connection of the design parameters of the conductivity of the regulated choke and changes in the temperature of the working fluid. The scientific novelty of this study is the proposed analytical dependence, reflecting the change in flow rate from the applied current strength (magnetic field). The refined mathematical model of the process of damping the knee joint prosthesis is developed. Keyword list: Damper, Prosthesis, Modeling in SolidWorks, Adaptive Properties, Choke. To study MRD, a package of applications "MatLab", in addition to "Simulink" was used. The results of the study allow to improve the design of the MP damper and reduce the temperature factor on its characteristics. Publications On the materials of the master's thesis 4 papers were published, namely 3 theses of reports at international scientific and technical conferences of students.
Магистерская диссертация на тему "Совершенствование эндопротеза коленного сустава за счет использования магнитно-реологического демпфера", состоит из __3__ разделов, объем пояснительной записки __121__ страниц у основного текста, включает _75__ рисунков и _31__ таблиц, и __8__ плакатов графического материала. Целью работы является повышение стабильности МРД протеза коленного сустава в изменяющихся условиях эксплуатации. Для достижения поставленной цели был сформулирован ряд задач: - провести анализ существующих конструкций протезов коленных суставов - теоретически обосновать и создать математические модели рабочих процессов и исследовать влияние температуры и напряженности магнитного поля на рабочие характеристики МРД; - разработать экспериментальную установку для проверки и уточнения математических моделей МРД; - провести экспериментальные исследования; - разработать рекомендации по созданию адаптивных демпферов с учетом результатов полученных при выполнении работы. Первый раздел данной работы посвящен аналитическому исследованию влияния внешних и внутренних факторов на демпферы протеза и методы адаптации в них. Вторая глава посвящена разработке математической модели описывающей зависимость влияния температуры на рабочую характеристику демпфера. Третий раздел включает в себя создание стенда для проведения соответствующих экспериментальных исследований, представлена схема и необходимая аппаратура, позволившие создать непосредственно стенд для исследований влияния температуры и давления рабочей среды на рабочие характеристики М РД сустава. Разработаны методы экспериментальных исследований. Проведено серии экспериментов, для определения влияния перепада давления и температуры на рабочую характеристику. Объектом исследования в данной работе является процесс функционирования МРД протеза коленного сустава, а именно его дросселя при различных условиях эксплуатации. Предметом исследования является связь конструктивных параметров проводимости регулируемого дросселя и изменения температуры рабочей жидкости. Научной новизной данного исследования предложенные аналитические зависимости, отражающие изменение расхода от приложенной силы тока (магнитного поля). Разработана уточненная математическая модель процесса демпфирования протеза коленного сустава. Перечень ключевых слов: Демпфер, протезирование, моделирование в SolidWorks, адаптивные свойства, дроссель. Для исследования МРД использовался пакет прикладных программ "MatLab", в приложении к нему "Simulink». Результаты исследования позволяют усовершенствовать конструкцию МР демпфера и уменьшить температурный фактор на его характеристики. Публикации. По материалам магистерской диссертации было опубликовано 4 работы, а именно 3 тезис а докладов на международных научно - технических конференциях студентов.

This master's thesis deals with an engineering design of an external reservoir for hydraulic shock absorbers with combined filling of oil and magnetorheological fluid. The first part describes existing designes of magnetorheological shock absorbers and characteristics of magnetorheological fluid. Next part describes a design of an experimental external reservoir and a test of its functionality on a prototype. This is followed by an optimalized engineering design of the experimental external reservoir.

The master thesis deals with design, manufacturing and testing of a prototype magnetorheological damper developed for Formula Student vehicle. The aim was to design and test the damper with similar damping properties to the vehicle as a conventional damper has. Target force-velocity curves were set using quarter car model and evaluated comparing minimal contact force of a tyre for conventional and newly developed damper characteristics. Structural analysis of designed parts, hydraulic and static magnetic analysis were performed. Manufacturing of a specific part magnetorheological damper part was described – piston. Manufactured prototype damper characteristics were evaluated.

This thesis features the development of a software program with a plot function (a setting bank) for data curves, obtained when car dampers are tested in a dynamometer, which measures forces at given velocities. Advanced dampers have many different adjusting possibilities and it was desired to collect data about this for a number of damper types, in a software program that can be used to predict damper curves without having to perform actual tests. The goal was to make it easier for customers (mostly consisting of competitions teams) to test and evaluate different settings to a chosen damper in a fast and simple way, without having to use expensive testing equipment that also is a big time consumer. The project was performed at Öhlins USA Inc. in Hendersonville, North Carolina. It is a subsidiary to Öhlins Racing AB, that manufactures performance shock absorbers for cars, motorcycles, snowmobiles and ATVs for both competition and commercial use. The project was initiated by evaluating and deciding different measuring methods, to see what equipment would be used and how the data collection would be performed. A literature study was also performed to get a better understanding about dampers and their functioning and anatomy. Work began by collecting empirical data at different velocities for a number of different settings, with a dynamometer. Because of the number of possible settings and the time elapse when collecting data, all settings were not actually collected. Most of them were instead calculated mathematically from the collected data. This resulted in data consisting of forces and velocities for a great number of damper settings. Both internal (when hardware in the damper is changed) and external (when changes are made to the hardware). When the data collection and the calculations were done, the software program itself was created with Microsoft Excel and Microsoft Visual Basic. The software lets the user select a damper type and its settings and then plot a graph that corresponds to the damper curve that would be obtained in a real testing rig. The results of the project was a working setting bank that can plot damper curves for a number of Öhlins damper models, by using the collected and calculated data. To increase the accuracy of the curves towards reference data, future studies might need to be performed which uses even better mathematical models and considers flow resistance in the damper.

As a racecar negotiates a track, it is subjected to many inputs at both high and low frequencies. These inputs come from the track surface, the motion of the body, and from aerodynamic disturbances. The damper's ability to control these inputs leads to improved grip at the tires, which increases overall handling of the vehicle. Since dampers have always been assumed to be primarily velocity dependent, little work has gone into exploring damperâ s frequency dependent nature. Therefore, this study evaluates the effect input frequency has on the damper's output force.

Utilizing experimental testing, with a state of the art damper dynamometer, and computer simulation with a parametric damper model developed for this study, several inputs and key parameters are tested, and the damper's frequency dependent nature starts to emerge. Constant peak velocity sinusoidal and sinusoidal sweep inputs are used for the experimental testing. The results show that as the input frequency is increased, the damper's output force lissajou transitions from the characteristic shape of a damper's lissajou to a shape characteristic of a spring's lissajou. This change in the lissajou is linked to hysteretic effects, which includes the gas spring effect. Damper parameters that are suspected to contribute to the hysteretic effects are explored with computer simulation and additional experimental testing. The results from this show that fluid preparation, fluid type, initial gas pressure, and friction have a predictable effect on the damper's output force.
Master of Science

This work is aimed to creating a system for presentation of oscilations. The main part consist of electromagnetic damper, which properties are suitable for use in this system. In the first part are some conditions for design of damper body . In he second part are selected next parameters for electromagnetic damper and of the whole system by MATLAB / Simulink with iterative method. In last part is whole system analyzed and the results indicate next changes in the structure of the system.

Damping in a multitude of engineering applications has a variable threshold requirement based on the input excitation given to the system. In most applications the desired system response is known but the input to the system is a time dependent function with fluctuating amplitudes and frequencies. Therefore for optimal performance the damping characteristics of a given system must be able to adapt to increase or decrease the amount of energy being absorbed by the system. In most mechanical systems (including vehicles) damping is achieved through a viscous medium; such as hydraulic oil. Although the oil is capable of absorbing the unwanted energy in the system, its passive nature limits its ability to achieve an optimal amount of damping given the excitation. To achieve the requisite functionality of variable damping; a multitude of solutions have been implemented, proposed, and evaluated at both commercial and academic research levels. These solutions have met the variable damping requirements but have significant cant drawbacks associated with them. To address the shortcomings associated with the aforementioned variable damping solutions, a hybrid design consisting of a conventional hydraulic damper and a linear motor topology was fused together to produce a hybrid variable damper. In this hybrid design, the oil in the system acts as bias and the linear motor topology allows for variability in the amount of damping being provided to the system. This hybrid design allows for the requisite variable damping requirement to be achieved. In addition to the hybrid design being able to achieve variable damping, it has the capacity to act as a generator and also provide fail-safe operation due to the viscous bias. Through analytical, FEM analysis and experimental modeling the hybrid damper has been characterized and with a high level of agreement between the various results. This work has also shown that the design is capable of achieving variable damping with the capacity to recover energy from the system.

碩士
國立臺灣大學
造船及海洋工程學研究所
89
Abstract This thesis is to explore the performance of a Shear-Mode Electro-Rheological (ER) Shock Absorber with a controllable damping force and to investigate its difference on decreasing vehicles’ shock from traditional shock absorbers. I use the quarter car model of a vehicle suspension system as the experiment foundation. Inside the shock absorber the ER fluids instead of hydraulic oils were used. The characteristic of ER fluids is continuity modulated as it will incorporate the controllable electric field in order to make the system to become so called Semi-Active Suspension System. At last under the proof of simulated data and result of the experiment , it will show the application works.

碩士
元智大學
機械工程學系
96
Recently, the Mac Pherson independent suspension systems have been adopted popularly on light sedans and luxury vehicles. This kind of design can overcome the space insufficiency problem for installing the upper links, such as that on those non-independent suspension systems, in the limited engine compartment. The design can also help to improve the true contact of tires with road surfaces when driving on rough roads. As a result, the system has advantages in providing better riding comforts by absorbing vibrations effectively. However, the oil leakage on some front struts is often observed in the Mac Pherson independent system after driving certain miles even it is still in guarantee period such as that on new cars. Thus, the spring suppliers always try to modify some of the spring parameters (e.g. pitch, length, and coils) to overcome this problem. They attempt to change these parameters based on their experiences while keeping design specifications. Later, it is followed by conducting a spring durability test for the validation purposes. For all these reason, this study aims to establish the optimal spring parameters for the above mentioned purposes based on fundamental theories and using the commercial software in finite element analysis. Besides, there are camber and caster angles designed on the independent suspension system for better control of the car on the following features: the steering wheel’s self-return function after turning, the straight-trace control when driving on a straight road, and the improvement of the tire’s contact with road surfaces. However, how these designed angles affect the offset of the resultant spring force are also investigated correspondingly. Hence, the presented results can provide the spring manufacturer better know-how on tuning the spring and improve the reliability of the spring on the suspension system.